fix(#799): quote the id value and refuse to insert when nothing was deleted

[Thayorns]

Fbe.delete_one built its delete query by interpolating the identifying value straight into the sentence, so a String value arrived at the parser as a bare word and was read as a property name. With a custom id: the query matched nothing, the delete removed nothing, and the rebuilt fact was inserted anyway, leaving the original next to a copy of it.

The value now goes through Fbe::Term, a small object that renders one (eq prop value) sentence with the value spelled the way the parser reads it back: a String in quotes with the quotes inside escaped, a Time in ISO 8601, everything else as it is. The same interpolation lives in Fbe.if_absent, Fbe.just_one, Fbe.delete and Fbe.overwrite; moving them onto this object is worth a separate issue.

The second half of the bug had nothing to do with quoting. delete! was called for its side effect and its answer thrown away, so handing delete_one a fact that does not live in the given factbase inserted a copy of it there. It now raises Fbe::Error when the delete matched no facts, the way Fbe.overwrite already does.

Closes #799

[Thayorns]

@yegor256 please take a look when you have a moment, happy to clarify anything here.

[yegor256]

This looks like the right fix for the quoting bug, but it's got conflicts with master now, so it needs a rebase before it can go in. Requesting another look too.

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[Thayorns]

@yegor256 done, ready for review again